1. Field of the Invention
The present invention relates to a microchip device for chemotaxis observation to observe a phenomenon called chemotaxis.
2. Related Background Art
Chemotaxis is a directional migration of cells in response to concentration gradients of chemical substances called chemotactic factors. The chemotaxis has been applied to development of therapeutic agents; especially, it is expected to open a new approach to development of cures for inflammation, allergy, and cancer. Chemotaxis studies therefore have increasing importance. In order to observe the chemotaxis, there is proposed use of a microchip for observing movement of the chemotactic factors. It is, for example, described in Nikkei Biotechnology and Business, November 2001: pp. 48-50.
The microchip, which will be referred to hereinafter as a microchip device for chemotaxis observation, is provided with a section in which chemotactic factors are to be filled, and a section in which chemotactic cells are to be filled. Between those sections are a number of narrow paths called a channel in a lattice arrangement. The width of the path is a little smaller than a general size of a cell. When concentration gradients of the chemotactic factors occur, cells move themselves toward a higher concentration through the paths. FIG. 8 shows a structure of a path in a conventional microchip device for chemotaxis observation. As shown in FIG. 8, a path 41 of the conventional microchip device is formed so that an island 42 stands as a sidewall thereof. A cross-sectional view along line B-Bxe2x80x2 is shown at the bottom of FIG. 8. As shown therein, the island 42 projects from a bottom surface of the path 41 at an obtuse angle of xcex1. In other words, the sidewall surface of the path 41 has the obtuse angle xcex1 to the bottom surface. The angle xcex1 is 54.7xc2x0, for example.
In the conventional microchip device for chemotaxis observation, however, the sidewall surface of the path 41 is sloped; thus, a slope 421 appears to be black when examining the chemotaxis with a microscope. The conventional microchip device for chemotaxis observation therefore has the problem that observation of the cells passing through the slope 421 is interfered with. Also, it has a problem that there is a limitation to the width of the path because narrower path causes restriction of the depth due to the slope.
As explained above, the conventional microchip device for chemotaxis observation has the problem that the slope of the sidewall surface of the path interferes with the cell observation and restricts the path width.
The present invention has been accomplished to solve the above problems and an object of the present invention is thus to provide a microchip device for chemotaxis observation which facilitates the cell observation and allows design freedom for the path width.
A microchip device for chemotaxis observation according to the present invention is provided with a first area in which chemotactic factors are to be filled, a second area in which chemotactic cells are to be filled, and a channel having a path communicating between the first area and the second area, wherein a sidewall surface of the path is substantially perpendicular to a bottom surface of the path.
The above path is configured by anisotropic dry etching in order to form the sidewall surface substantially perpendicular to the bottom surface of the path. The sidewall surface of the path is thus not sloped; therefore, it does not interfere with the observation. Besides, the anisotropic dry etching makes it possible to form paths of various shapes including circular, elliptical, triangular, and L-shape, as well as linear shape. It is also makes it possible to form a path having the width that is so microscopic as to be defined by a photomask, thereby enabling observation of smaller cells and miniaturization of the microchip. Further, the dry etching provides high repeatability while wet etching has low repeatability to produce various amount of side etching.
The anisotropic dry etching is preferably inductively coupled plasma reactive ion etching (ICP-RIE).
In a preferred embodiment, the microchip device for chemotaxis observation is composed of a silicon wafer.
A manufacturing method of a microchip device for chemotaxis observation according to the present invention is a method of manufacturing a microchip device for chemotaxis observation provided with a first area in which chemotactic factors are to be filled, a second area in which chemotactic cells are to be filled, and a channel having a path communicating between the first area and the second area, wherein the channel is formed by anisotropic dry etching. A sidewall surface of the path formed by the anisotropic dry etching is not sloped; therefore, it does not interfere with the observation. Besides, the anisotropic dry etching makes it possible to form paths of various shapes including circular, elliptical, triangular, and L-shape, as well as linear shape. It is also makes it possible to form a path having the width that is so microscopic as to be defined by a photomask, thereby enabling observation of smaller cells and miniaturization of the microchip. Further, the dry etching provides high repeatability while wet etching has low repeatability to produce various amount of side etching.
The microchip device for chemotaxis observation is provided with a penetration hole through which the chemotactic factors and the chemotactic cells are filled. The penetration hole is preferably formed by the anisotropic dry etching. It solves the problem that etching damages a wall surface of the penetration hole to injure cells, thereby allowing effective experiments. It also facilitates alignment of the penetration hole to simplify manufacturing processes.
The anisotropic dry etching is preferably inductively coupled plasma reactive ion etching.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.